1. Field of the Invention
The present invention pertains in general to the electro-optical art and more particularly to an apparatus utilizing non-linear optical organic polymers for applying a phase shift to deflect an optical beam.
2. Description of the Prior Art
Systems for deflecting a beam of radiant energy under the control of an electrical signal are well known in the art. For example, acousto-optical deflection systems consist essentially of a bar of elastic material whose refractive index is modulated by means of an ultrasonic wave coming from an electro-mechanical transducer affixed to one of the ends of the bar. When an electrical control signal is applied to the transducer, the refractive index of the body of the bar is caused to vary, thereby producing a phenomenon of optical refraction. By changing the frequency of the ultrasonic signal, more or less refraction may be observed in the modified direction of the reflected beam. However, typically, an acousto-optical cell has a coefficient of optical refraction such that the deflection range is limited to a few degrees. Further, such systems require a substantial amount of ultrasonic power to create in the acousto-optical cell the appropriate energy density, and complex optical systems to increase the deflection range. Typical of the acousto-optic devices is U.S. Pat. No. 4,415,226, Apparatus For Controlling Light In Electro-Optic Wave Guides With Individually Addressable Electrodes.
Beam steering based on alterable magnetic stripe domains in an epitaxial layer has been described in U.S. Pat. No. 3,752,563, Magnetic Film Stripe Domain Diffraction. In that invention, a magneto-optic light deflection system utilized the stripe domains in a magnetic film as a diffraction grating. The angle of deflection of the light from the plane of the film is varied in two dimensions by varying the separation and orientation of the stripe domains. Means are provided to vary the separation of adjacent domain walls, i.e., the width of the stripe domains, and the rotatable orientation of the parallel stripe domains. The resulting system is utilized to control, by the Kerr or Farady effect, the focus of a light beam that is directed upon the plane of the film. Magnetic stripe domain structures are operative over a limited wavelength and field of view, with an efficiency between ten and thirty percent and a divergence of the order of two milliradians. In addition to being wavelength dependent, magneto-optic deflectors have a limited response range typically of the order of 0.1 to 100 microseconds.
An electro-optical technique has been described in Optic News, April, 1989, page 34. This brief report provides little technical data and describes the use of metal-organic chemical vapor deposition techniques to grow alternating layers of compound semi-conductors such as GaAs and GaAlAs to serve as thin electro-optically active optical waveguide sandwiched between thicker electrically conducting buffer layers that are also optically transparent. Electrical connections to the buffer layers allow the variation of the time delay of the optical radiation propagating through the electro-optical guide layers. By computer controlling a large number of these time-variable optical guides, an optical phased array device was obtained for electrically scanning or positioning a laser beam.
Liquid crystal deflectors have also been applied for optical beam deflection, as in Liquid Crystal Adaptive Lens: Beam Translation and Field Meshing, Applied Optics, Vol. 27, pp. 4578-4586, Nov. 1, 1988. The article describes a design in which a parabolic voltage profile is applied to an array of interdigital electrodes on one side of a liquid crystal cell. The index of refraction of the cell is altered in a prescribed manner with the net effect that an optical beam passing therethrough is translated perpendicular to the direction of propogation.
The present invention provides an improved electro-optical deflection apparatus utilizing layers of non-linear optical organic polymers electrically controlled to form a phased array. It is operative over wavelengths from the ultraviolet to the far infra-red. Greater than ninety percent of the incoming energy is deflected. By cascading two deflectors, a field of view up to ninety degrees by ninety degrees may be obtained. Divergence is dependent on the number of NLO layers, with more layers providing less divergence. The NLO material can respond to frequencies up to 10.sup.15 Hz; therefore, the speed is determined and limited only by the control electronics.